The present invention relates to engines having hydraulically-actuated fuel injection systems and, more specifically, to pumping systems for such engines.
Internal combustion engines equipped with a hydraulically-actuated fuel injection system (HEUI fuel system) employ an actuating pump to provide actuating fluid at elevated pressures to injectors, thus elevating the pressure of the fuel being injected into the engine. Control of the fuel injection pressure is achieved by controlling the pressure of the actuating fluid, hereinafter referred to for convenience simply as xe2x80x9coil.xe2x80x9d Typically, control of the oil pressure is achieved by employing a fixed displacement pump to elevate the fluid pressure and regulating that pressure to lower levels by bleeding off unneeded flow volume through a rail pressure control valve (RPCV), past which the unneeded oil returns to a sump or reservoir.
In conventional HEUI systems, the pump, RPCV and reservoir are physically associated so as to form, in effect, a single unit which is mounted to the engine. Oil at low pressure is supplied from the engine to the pump through hydraulic tubing connected by suitable fitting to the engine and to the low pressure inlet of the pump. After elevation of pressure by the pump, the oil passes through the RPCV, and thence back to the reservoir or, through additional hydraulic tubing, to the high pressure manifold (rail).
Examples of hydraulically-actuated fuel injection systems are shown in U.S. Pat. No. 5,191,867 issued to Glassey, et al on Mar. 9, 1993, and U.S. Pat. No. 5,213,083 issued to Glassey on May 25, 1993; a variable-displacement pump for an HEUI fuel system is shown in U.S. Pat. No. 5,515,829 issued to Wear, et al on May 14, 1996, all of which are assigned to the assignee of the present invention. Pumps for HEUI fuel systems, as well as other rotary, engine-operated pumps, e.g., power steering pumps, typically have a pump shaft which is coupled to the engine crankshaft by appropriate connecting mechanism. Such a pump, mounted to a bracket and spaced forwardly of the engine and terminal end of the crankshaft, is shown in U.S. Pat. No. 3,927,954 issued to Walker on Dec. 23, 1975. This patent also shows a cylindrical housing with external belt grooves mounted upon the crankshaft between the engine and the pump and partially enclosing the pump.
The present invention is directed to solving various packaging and placement problems that occur when placing an HEUI system on a relatively small engine. Additionally, the invention is directed to providing a more cost effective and aesthetically improved design, and to overcoming one or more of the problems or concerns set forth above.
The present invention physically separates the three main components, namely the pump, the RPCV and the reservoir, of the HEUI system. The pump is mounted in encircling relation to the engine crankshaft for direct drive of the movable pump components which are keyed to the crankshaft. The low pressure inlet and high pressure outlet of the pump communicate directly with internal passages in the engine block, thus eliminating the need for hydraulic tubing between the pump and engine. Also, the inlet and outlet of the RPCV communicate directly with the engine block passages. Cold start oil volume in the rail is provided by mounting the reservoir at a slightly higher elevation than the rail instead of by a diaphragm mechanism in the pump. Further features are the provision of a hydrostatic thrust bearing to carry the thrust load of both sides of the wobble plate, and the mounting of other components, including a cylindrical housing with pulley grooves on its outer surface substantially enclosing the pump housing, on the crankshaft end extending through the pump.